1. Field of the Invention
The present invention relates to treatment of louse infestations, and in particular to monitoring and affecting the course of such treatment.
2. Description of the Related Art
Lice represent an increasingly prevalent social and health problem in many countries, including the United States. Lice spread rapidly by contact; infestations can therefore occur even under relatively sanitary conditions and, given the ease of modern travel and immigration, appear even in normally pest-free environments.
Lice infest both humans and animals. They produce irritations typically experienced as uncomfortable local itching and burning, occupying regions under matted fur (in animals) and the ears, head, neck and shoulders (in humans). More serious infestations can cause infection, anemia and fever. Three major diseases--epidemic typhus, trench fever and relapsing fever--are transmitted by lice. The species most troublesome to humans are the head lice Pediculus capitis or Pediculus humanus capitis; the body or clothing lice Pediculus humanus humanus or Pediculus corporis; and the pubic lice Phthirius pubis.
The parasites themselves are insects that are very small (two to three millimeters in length) and not easily observed without magnification. They attach themselves to hair and fur shafts near the bases, where they lay eggs, frequently called "nits," that become firmly attached to hair and fur through an adhesive excretion. The eggs resemble white gains of sand and are easily mistaken for dandruff; at body temperature, they generally hatch in eight to 10 days. Because of the small size of the louse and its nits, detection by visual inspection can be difficult. The difficulty increases as treatment progresses and the concentration of visually apparent particles decreases.
Numerous methods of treatment have been devised to combat louse infestations; unfortunately, even when fully effective, these tend to result in side effects, and are at the very least inconvenient and expensive. Accordingly, determining when the lice have been fully eliminated can avoid needless prolongation of harsh treatments. Likewise, detecting infestations or re-infestations (which can occur, for example, from wearing an infested garment) at the earliest possible stage will minimize the duration of treatment.
The most common form of treatment is the frequent use of an insecticidal shampoo that is toxic both to the louse and the egg. The harsh nature of the active ingredients in such preparations, however, can prevent or restrict their use by certain susceptible individuals and very young children; moreover, the lice themselves can build up resistance to insecticidal products even during the course of treatment, necessitating prolonged application that can cause discomfort even in adults. Head lice are also treated using heated or electrically charged hair combs; see, e.g., U.S. Pat. No. 5,261,427. The efficacy of these approaches typically depends on physical contact between the comb and the lice and/or eggs, requiring extensive applications that can irritate the human scalp.
Thus, using current techniques, the treatment agent is applied to the infestation for a fixed period that is sufficiently long to ensure the probable eradication of the infestation--regardless of the actual severity of that infestation, the susceptibility of the particular lice to treatment, or the adverse effects of treatment on the individual. While the mere existence of an infestation can be detected by visual inspection, such inspection cannot indicate the infestation's extent or the optimal amount of treatment to eradicate it. There is, accordingly, a long-felt and heretofore unmet need for limiting the course of treatment for louse infestations to the extent possible while assuring overall treatment efficacy.